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이추실(Q. S. Li),이민철(M. C. Lee),정동찬(D. C. Jung),손요헌(Y. H. Son),전만수(M. S. Joun) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.10
In this paper, effects of major design parameters of cold forging dies on die mechanics are quantitatively investigated with emphasis on shrink fit using a thermoelastic finite element method. A ball-stud cold forging process found in a cold forging company is selected as a test process and the effects of die insert material, shrink fit, dimension of ring, partition of die inert and clamping force on effective stress and circumferential stress are analyzed.
이추실(Q. S. Li),김민철(M. C. Kim),최영묵(Y. M. Choi),김영수(Y. S. Kim),손요헌(Y. H. Son),전만수(M. S. Joun) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.5
In this research, a feasibility study on manufacture of high strength bolt-form products by cold forging is carried out. Problems from standpoint of material, process design, and die design are investigated in detail using finite element analysis. It is noted that strain-hardening capability should be relatively low in forging of high strength material to keep material strength not so much high and that strain-hardening capability has a great influence on metal flow or deformed shape as well as accumulated damage. Two failure cases of developing high strength bolts are introduced and investigated in detail with their forging simulation results.
축대칭 냉간압출공정에서 공정변수 및 재료의 변형경화지수와 손상도의 상관관계
이추실(Q. S. Li),김민철(M. C. Kim),손요헌(Y. H. Son),전만수(M. S. Joun) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.5
In this paper, relationship between damage accumulation and process parameters and material properties including strain hardening exponent in axi-symmetric cold extrusion is presented in detail. A rigid-plastic finite element method is employed for this study. Reduction ratios ranging from 10% to 40%, die angles ranging from 10° to 20°, and strain hardening exponents ranging from 0.00 to 0.25 are investigated with emphasis on their relationship with the maximum damage values accumulated along the central lines. It has shown that the strain hardening exponents have very strong influence on the damage accumulation and the shape of extruded end.
고강도 재료위 볼스타드 냉간자동단종에서 발생한 금형의 파괴 원인 분석
이추실(Q. S. Li),엄재근(J. G. Eom),김영수(Y. S. Kim),김응주(E. J. Kim),전만수(M. S. Joun) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.10
In this paper, a longitudinal die insert fracture which occurred during cold forging cold forging of a high strength ball-stud with a sound die design nearly optimized empirically for relatively low strength material of SCM435 is introduced and the reason is revealed. A comparative study between SCM435 and ESW105 is quantitatively made using a thermoelastic finite element method for die structural analysis coupled with a forging simulator theoretically based on a rigid-plastic finite element method. It has been shown that the longitudinal die insert fracture caused from non-optimized value of shrink fit, emphasizing that the die optimal design is inevitable for cold forging of high strength materials.
열간 알루미늄 롤단조 공정의 유한요소해석과 실험적 검증
엄재근(J. G. Eom),이추실(Q. S. Li),이민철(M. C. Lee),전만수(M. S. Joun),정순종(S. J. Jung),박건형(G. H. Park),곽양섭(Y. S. Gwak) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
In this paper, an aluminum ring forging process of manufacturing an optimizes perform for a hot forging process is simulated using AFDEX 3D, a general-purpose metal forming simulator based on rigid-thermoviscoplastic finite element method. Non-isothermal analysis is carried out and the predictions are compared with the experiments in terms of dimensional accuracy. It was shown that the predictions are in good agreement with the experiments.
냉간전방압출공정 중에 발생한 중심파괴 현상의 유한요소해석
김민철(M. C. Kim),이추실(Q. S. Li),손요헌(Y. H. Son),윤덕재(D. J. Yoon),전만수(M. S. Joun) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
In this paper, a new scheme for simulating the central bursting defect formation occurred during cold forward extrusion is presented. The scheme is implemented onto AFDEX 2D, based on a rigid-thermoviscoplastic finite element method. A element removal scheme after separating or cracking the damaged neighboring elements along the element boundary is proposed. Fracture model with fracture criterion are introduced considering both cumulative damage and the maximum principal stress. The results show that more realistic shape of the chevron crack was obtained with the new criterion.
엄재근(J. G. Eom),이추실(Q. S. Li),장성민(S. M. Jang),안순태(S. T. Ahn),손요헌(Y. H. Son),현성운(S. W. Hyun),김혁(H. Kim),윤덕재(D. J. Yoon),전만수(M. S. Joun) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
In this paper, plastic deformation behaviors of ESW105 and SCM435 steels are revealed by simulations and experiments. ESW105 is the special pre-heat-treated steel characterized by high initial yield strength and negligible strain-hardening behavior. The flow stresses of the two steels for large stain are calculated from tensile tests. Axial and lateral compressions of cylindrical bars are tested and simulated and the deformed shapes are compared to characterize the plastic deformation behaviors of the two materials. A forward extrusion process of a cylindrical bar is also simulated to reveal the difference. It has been shown that there are pretty much difference in plastic flow between ESW105 and SCM435 which causes from the difference in strain-hardening capability, implying that the experience-oriented design rules for common commercial materials may lead to failure in process design when the new material of ESW105 is applied without consideration of its plastic deformation behavior.